从视图中获取当前活动、片段、LifeCycleOwner 的简单方法？

Question

编写时Views，ViewModels并且LiveData具有生命周期意识。在ViewModel想是目前的FragmentActivity，LiveData当前的LifecycleOwner。您事先不知道您的 View 是否会被包裹或有所包裹。所以它需要一个灵活的函数来找到想要的上下文。我最终采用了这两种方法：

private FragmentActivity getFragmentActivity() {
    Context context = getContext();
    while (!(context instanceof FragmentActivity)) {
        context = ((ContextWrapper) context).getBaseContext();
    }
    return (FragmentActivity) context;
}

private LifecycleOwner getLifecycleOwner() {
    Context context = getContext();
    while (!(context instanceof LifecycleOwner)) {
        context = ((ContextWrapper) context).getBaseContext();
    }
    return (LifecycleOwner) context;
}

现在这是要放入每个视图的大量样板代码。有没有更简单的方法？

我不想为此使用自定义的 View 基类，因为大的层次结构很难看。另一方面，组合需要与此解决方案一样多的代码。

Answer 1

你可以找到它 lifecycle-runtime-ktx：

fun View.findViewTreeLifecycleOwner(): LifecycleOwner? = ViewTreeLifecycleOwner.get(this)

Answer 2

Kotlin 扩展

fun Context.fragmentActivity(): FragmentActivity? {
    var curContext = this
    var maxDepth = 20
    while (--maxDepth > 0 && curContext !is FragmentActivity) {
        curContext = (curContext as ContextWrapper).baseContext
    }
    return if(curContext is FragmentActivity)
        curContext
    else
        null
}

fun Context.lifecycleOwner(): LifecycleOwner? {
    var curContext = this
    var maxDepth = 20
    while (maxDepth-- > 0 && curContext !is LifecycleOwner) {
        curContext = (curContext as ContextWrapper).baseContext
    }
    return if (curContext is LifecycleOwner) {
        curContext as LifecycleOwner
    } else {
        null
    }
}

用法

val lifecycleOwner = context.lifecycleOwner()
val fragmentActivity = context.fragmentActivity()